ZyXEL Communications USG-300 - V2.20 ED 2 Manual page 514

Chapter 25 IPSec VPN
• SNAT - the translated source address; a different IP address (range of
addresses) to hide the original source address.
Destination Address in Inbound Packets (Inbound Traffic, Destination
NAT)
You can set up this translation if you want the ZyWALL to forward some packets
from the remote network to a specific computer in the local network. For example,
in Figure 368 on page
forward mail from the remote network to the mail server in the local network (A).
You have to specify one or more rules when you set up this kind of NAT. The
ZyWALL checks these rules similar to the way it checks rules for a firewall. The
first part of these rules define the conditions in which the rule apply.
• Original IP - the original destination address; the remote network (B).
• Protocol - the protocol [TCP, UDP, or both] used by the service requesting the
connection.
• Original Port - the original destination port or range of destination ports; in
Figure 368 on page
The second part of these rules controls the translation when the condition is
satisfied.
• Mapped IP - the translated destination address; in
IP address of the mail server in the local network (A).
• Mapped Port - the translated destination port or range of destination ports.
The original port range and the mapped port range must be the same size.
514
513, you can configure this kind of translation if you want to
513, it might be port 25 for SMTP.
Figure 368 on page 513, the
ZyWALL USG 300 User's Guide